US4971625A - Method for leaching gold and/or silver out of ores or out of ore-concentrates and also out of precious-metal wastes or precious-metal scrap by using cyanide-containing leaching solutions - Google Patents

Method for leaching gold and/or silver out of ores or out of ore-concentrates and also out of precious-metal wastes or precious-metal scrap by using cyanide-containing leaching solutions Download PDF

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Publication number
US4971625A
US4971625A US07/292,239 US29223988A US4971625A US 4971625 A US4971625 A US 4971625A US 29223988 A US29223988 A US 29223988A US 4971625 A US4971625 A US 4971625A
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leaching
flow
solution
slurry
cyanide
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US07/292,239
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English (en)
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Albert Bahr
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Evonik Operations GmbH
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Degussa GmbH
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B11/00—Obtaining noble metals
    • C22B11/08—Obtaining noble metals by cyaniding
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • the invention relates to a method for recovering precious metal components by leaching gold and/or silver out of ores or ore-concentrates and also out of precious-metal wastes or precious-metal scrap.
  • Method for recovery of the precious metal values employs cyanide-containing leaching solutions having a pH value between 7 and 13 by adding an aqueous H 2 O 2 solution.
  • the starting material is finely ground and dispersed in water to form a slurry.
  • the pH value of the ore slurry is then raised into the alkaline pH range by adding lime or milk of lime, whereupon the complexforming cyanide is added, as a rule in the form of NaCN in an aqueous solution of approximately 5 to 20%.
  • the ore slurry is agitated, with introduction of air, for 24 to 48 hours in stirring tanks or Pachuca tanks for a time period of 24 to 48 hours.
  • the pH value of the ore slurry must be raised into the alkaline range and be kept there. Ordinarily, the process takes place in the pH range from 10 to 11. Typically, this pH range is set by adding lime and milk of lime in the ratio of 80:20.
  • the cyanide concentration of the ore slurry depending on the ore composition ranges from 0.025 to 0.25 % by weight of NaCN.
  • the cyanide is metered in the form of an aqueous solution of 2 to 20 % into the first of up to ten cascaded leaching tanks traversed by the slurry.
  • a concentration of dissolved oxygen in the slurry is chosen to be as close as possible to the physically determined maximum value of about 8 to 9 ppm because at the practicable conventional cyanide concentration of 0.3 to 3 kg/ton of ore, the diffusion of the dissolved oxygen in the slurry determines the rate of leaching.
  • KCN also may be used just as well.
  • the molar ratio of NaCN/H 2 O 2 set in the above known procedure indicates that operation takes place at a pH value between 9.5 and 11.5 as in the previously described detoxification of the leaching slurries. Because of the marked decomposition of the NaCN in its reaction with the added H 2 O 2 only that NaCN added in excess is available for complexing the precious metals.
  • German patent 36 37 082 describes a procedure for the leaching of gold and/or silver out of ores or oreconcentrates employing an aqueous cyanide leaching solution with a pH of 8 to 13 and adding an aqueous solution of H 2 O 2 .
  • this prior process is carried out by controlling the addition of said H 2 O 2 solution by means of the concentration of the oxygen dissolved in the leaching solution, the oxygen content in said solution being set at 2 to 20 mg/liter.
  • the purpose thereof is to carry out the leaching more 0 economically, in particular by reducing the H 2 O 2 consumption, without thereby entailing higher sodium cyanide consumption relative to the previously known leaching with air blowing.
  • the object of the invention is to provide an improved leaching process and to appreciably shorten the leaching time relative to the known procedure while operating at the conventional NaCN concentration in the leaching slurry and with low consumption of H 2 O 2 , whereby also the costs of carrying out the method shall be significantly lowered.
  • the invention is based on the discovery that the reaction between NaCN and H 2 O 2 is strongly inhibited, that is it takes place more slowly in the alkaline pH range below 10 or above 11 and up to 13.
  • the NaCN is maintained as a complexing agent while simultaneously the desired concentration of dissolved oxygen in the slurry is obtained by the decomposition of the H 2 O 2 as required for the reaction between the NaCN and the precious metal as explained initially above.
  • an optimal ratio of H 2 O 2 concentration to the amount of precious metal to be leached and to the NaCN concentration is achieved over the entire leaching time.
  • the leaching slurry contains the highest amounts of precious metals to be leached and the highest amounts of cyanide.
  • the contents in H 2 O 2 in the leaching slurry automatically adjust themselves to the lessened demand.
  • the hydrogen-peroxide solution In order to accelerate the leaching process, it is necessary that as soon as the H 2 O 2 solution is introduced, it be homogeneously dispersed in the leaching slurry because otherwise local detrimental molar ratios NaCN/H 2 O 2 will occur in this leaching slurry which would result in accelerated decomposition of the NaCN whereby either the output of precious metals would be lowered or the necessary addition of NaCN would be increased. Accordingly, it is advantageous for the hydrogen-peroxide solution to be added continuously and homogeneously dispersed across the cross-section of a flow of leaching slurry.
  • the H 2 O 2 solution can be added to the leaching slurry both before or after the cyanide is added.
  • the addition of the H 2 O 2 solution is added before the cyanide is introduced into the leaching slurry because thereby an O 2 enrichment and dispersion in the slurry can be achieved before the cyanide addition.
  • the NaCN concentration is about 0.25 to 1 g per liter of the leaching slurry. It was ascertained by a series of tests that when liter of leaching slurry at a pH of 9, almost 100% of the precious metals can be extracted from this slurry after about 100 minutes. The precious metals can be separated in problem-free manner by charcoal adsorption.
  • the new method reduces the time for leaching precious metals to 1/5 to 1/20 of the times needed by the conventional procedures of the state of the art. Instead of the previous leaching times of 24 to 48 hours times of 2 to 4 hours are sufficient when using the new method.
  • the amount of the added H 2 O 2 solution is not limited by the quantity of NaCN present in the leaching slurry. Rather the H 2 O 2 amount may be clearly higher than that required for complete decomposition of the NaCN, without having to incur an undesired decomposition of the NaCN. Practice has shown it is advantageous to add the H 2 O 2 solution in such a quantity that the amount of the H 2 O 2 is 0.1 to 2.5 kg per ton of ore, for typical cyanide concentrations of 0.1 to 3 kg of NaCN per ton of ore.
  • An advantageous mode of introduction of the H 2 O 2 solution into the flow of leaching slurry is carried out by feeding the H 2 O 2 solution crosswise to this flow of leaching slurry at 10 to 50 times the flow rate of the flow of leaching slurry.
  • a preferred mode of implementation is characterized in that the leaching slurry is guided at a rate of 1 to 3 meters/sec. in the feed region of the H 2 O 2 solution and, further, in that the cross-flow of the H 2 O 2 solution is set for a rate of 10 to 100 meters/sec.
  • the feed of the H 2 O 2 solution into the flow of leaching slurry is carried out by conventional feed devices, preferably by slit-nozzles dimensioned in the micron range.
  • uniform dispersion of the H 2 O 2 into the flow of the leaching slurry is achieved within fractions of a second.
  • slit apertures of 5 to 100 microns are recommended if the H 2 O 2 solution is added to the leaching slurry in the area of tubular cross-section having a diameter no larger than 10 cm.
  • flotation reagents or anionic polymers in amounts of 5 to 1,000 g per ton of ore, preferably 25 to 250 g per ton, to the leaching slurry, in order to passivate or sequester the copper or iron minerals.
  • the addition of the flotation reagents or polymers takes place after the pH has been set in the leaching slurry, or before the H 2 O 2 solution and the cyanide are added.
  • Preferred sequestering or passivating agents are thiocarbonates, thiophosphates, thiocarbamates or anionic polymers in the form of acrylates, starches, and carboxymethyl cellulose.
  • the passivating or sequestering agents as a rule are added in the form of a 0.1 to 10 % by weight aqueous solution to the leaching slurry. Any suitable agent of this type can be used for purposes of the invention.
  • reagents as described herein advantageously should also take place in homogeneously dispersed manner over the cross-section of the slurry flow.
  • aqueous solutions this can be carried out using slit-nozzles, as already discussed in relation to the feed of the H 2 O 2 .solution
  • the homogeneous or short-term dispersion of the passivating of sequestering agents results in shortening their reaction times with Cu or Fe minerals respectively.
  • a gold ore rich in malachite/azurite (this is the leaching residue of a shut down gold-processing plant) contains about 3 ppm gold and 1.2 % copper as an important accompanying element.
  • the gold ore is ground to a d 80 value of 200 microns.
  • the ore is leached at a slurry density of 500 g of ore per liter of leach while being agitated with turbulence and with addition of NaCN between 0.02 to 0.2 % by weight.
  • the pH values of the leaching slurries are varied between 9 and 12.
  • H 2 O 2 solution 0.6 ml of 35% H 2 O 2 solution per liter of leach is fed through slit-nozzles, before the introduction of the NaCN, to the ore slurry having a density of 500 g of ore per liter of leach. This is carried out in such a way that a NaCN concentration of the leach of 0.05 % by weight is obtained.
  • the H 2 O 2 concentration of the leach is 0.02 % by weight.
  • the ore ground to a d 80 value of 200 microns is reacted at a slurry density of 500 g of ore per liter of leach with 0.7 kg NaCN per ton of ore and is aerated by air being blown in.
  • the slurry pH was set at 11.
  • the slurry of (C) with the same amount of NaCN and after its pH value has been set to 9 receives the peroxide solution until the amount of H 2 O 2 per ton of ore is 1.6 kg.
  • the slurry density was 500 g of ore per liter of leach and the addition of NaCN was 0.8 kg per ton of ore.
  • the H 2 O 2 solution was added until 1 kg of H 2 O 2 was present per ton of ore.
  • the Table shows that absent passivating sequestering the copper and iron sulfide, only a gold extraction of a maximum of 68 % is possible at a slurry pH of 11 and only of 55 % at a slurry pH of 9, and that further addition of H 2 O 2 takes place, whereas an increase in extraction is achieved already after leaching for 3 h up to 97% when adding the said passivating sequestering reagents.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacture And Refinement Of Metals (AREA)
US07/292,239 1988-01-22 1988-12-30 Method for leaching gold and/or silver out of ores or out of ore-concentrates and also out of precious-metal wastes or precious-metal scrap by using cyanide-containing leaching solutions Expired - Fee Related US4971625A (en)

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DE3801741 1988-01-22
DE3801741A DE3801741C1 (enExample) 1988-01-22 1988-01-22

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US (1) US4971625A (enExample)
EP (1) EP0327695B1 (enExample)
AR (1) AR240176A1 (enExample)
AU (1) AU604389B2 (enExample)
BR (1) BR8900199A (enExample)
DE (1) DE3801741C1 (enExample)
NZ (1) NZ227675A (enExample)
PH (1) PH26633A (enExample)
ZA (1) ZA89137B (enExample)

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU633203B2 (en) * 1990-06-02 1993-01-21 Degussa A.G. A process for leaching gold and silver
US5215575A (en) * 1989-03-07 1993-06-01 Butler Dean R Recovery of gold, silver and platinum group metals with various leachants at low pulp densities
US5250272A (en) * 1988-09-09 1993-10-05 Degussa Aktiengesellschaft Process for leaching precious metals with hydrogen-peroxide and a cyanide leaching solution
US5275791A (en) * 1986-10-31 1994-01-04 Degussa Aktiengesellschaft Process for the leaching of gold and silver with cyanidic leaching solution and controlled addition of hydrogen peroxide
US5336474A (en) * 1990-06-02 1994-08-09 Degussa Aktiengesellschaft Process for leaching of precious metals
US5368830A (en) * 1992-10-15 1994-11-29 Calgon Corporation Scale control in gold and silver mining heap leach and mill water circuits using polyether polyamino methylene phosphonates
AU656899B2 (en) * 1990-08-16 1995-02-23 University Of The Witwatersrand Determining cyanide concentration
WO1997044793A1 (en) * 1996-05-21 1997-11-27 British Nuclear Fuels Plc Decontamination of metal
US5961833A (en) * 1997-06-09 1999-10-05 Hw Process Technologies, Inc. Method for separating and isolating gold from copper in a gold processing system
ES2163948A1 (es) * 1998-07-14 2002-02-01 Consejo Superior Investigacion Procedimiento hidrometalurgico para la recuperacion de oro de minerales y materiales metalicos.
US6355175B1 (en) 1997-06-09 2002-03-12 Hw Process Technologies, Inc. Method for separating and isolating precious metals from non precious metals dissolved in solutions
US6406675B1 (en) * 2000-09-13 2002-06-18 Hercules Incorporated Method for reducing cyanide consumption during processing of gold and silver ores to remove base metals
US20050067341A1 (en) * 2003-09-25 2005-03-31 Green Dennis H. Continuous production membrane water treatment plant and method for operating same
RU2380434C1 (ru) * 2008-10-03 2010-01-27 Институт химии Дальневосточного отделения Российской академии наук (статус государственного учреждения) (Институт химии ДВО РАН) Способ извлечения золота из золотосодержащего органического сырья

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1990013676A1 (en) * 1989-04-28 1990-11-15 Cra Services Limited Recovery of gold and silver from complex refractory sulphide ores by cyanidisation and oxidation with peroxides
CA2051698C (en) * 1989-04-28 1997-12-30 Trevor John Smith Recovery of gold and silver from complex refractory sulphide ores by cyanidisation and oxidation with peroxides
ES2038535B1 (es) * 1991-06-14 1994-04-01 Riotinto Minera Sa Procedimiento para la recuperacion hidrometalurgica de metales no ferreos en cenizas de piritas.
RU2168555C2 (ru) * 1999-01-22 2001-06-10 ООО Артель "Восточная" Способ и устройство для выщелачивания богатых золотосодержащих концентратов
RU2167950C2 (ru) * 1999-07-15 2001-05-27 Открытое акционерное общество "Иргиредмет" Способ извлечения благородных металлов

Citations (7)

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US732605A (en) * 1902-11-18 1903-06-30 Gustav E Thede Process of leaching ores.
US3203968A (en) * 1959-06-03 1965-08-31 Sebba Felix Ion flotation method
US3339730A (en) * 1962-07-14 1967-09-05 Column Flotation Co Of Canada Froth flotation method with counter-current separation
US3826723A (en) * 1972-07-13 1974-07-30 Elmet Inc Process for recovering gold and silver
US4421724A (en) * 1981-09-08 1983-12-20 Anglo Mineral Resources, Inc. Extraction method for refractory precious metal ore
CA1221842A (en) * 1983-06-03 1987-05-19 Arthur E. Coburn Treatment of ores
US4786318A (en) * 1986-08-14 1988-11-22 Nalco Chemical Company Thickening of gold process slurries

Family Cites Families (1)

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DE3637082C1 (de) * 1986-10-31 1988-05-19 Degussa Verfahren zur Laugung von Edelmetallen aus Erzen oder Erzkonzentraten mit cyanidischen Loesungen unter Zusatz von Wasserstoffperoxid

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US732605A (en) * 1902-11-18 1903-06-30 Gustav E Thede Process of leaching ores.
US3203968A (en) * 1959-06-03 1965-08-31 Sebba Felix Ion flotation method
US3339730A (en) * 1962-07-14 1967-09-05 Column Flotation Co Of Canada Froth flotation method with counter-current separation
US3826723A (en) * 1972-07-13 1974-07-30 Elmet Inc Process for recovering gold and silver
US4421724A (en) * 1981-09-08 1983-12-20 Anglo Mineral Resources, Inc. Extraction method for refractory precious metal ore
CA1221842A (en) * 1983-06-03 1987-05-19 Arthur E. Coburn Treatment of ores
US4786318A (en) * 1986-08-14 1988-11-22 Nalco Chemical Company Thickening of gold process slurries

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
Davidson, R. J. et al. "The Intensive Cyandation of Gold-Plant Gravity Concentrates", J. of S. African Inst. of Min. and Met., Jan. 1978 pp. 146-165.
Davidson, R. J. et al. The Intensive Cyandation of Gold Plant Gravity Concentrates , J. of S. African Inst. of Min. and Met., Jan. 1978 pp. 146 165. *
Day, E. L. "Some Factors Influencing the Rate of Dissolution of Gold in Sodium Cyanide Solutions", Presented at Annual Meeting of Canadian Gold Metallurgists, Ottawa, Jan. 17-19, 1967, pp. 55-60.
Day, E. L. Some Factors Influencing the Rate of Dissolution of Gold in Sodium Cyanide Solutions , Presented at Annual Meeting of Canadian Gold Metallurgists, Ottawa, Jan. 17 19, 1967, pp. 55 60. *

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5275791A (en) * 1986-10-31 1994-01-04 Degussa Aktiengesellschaft Process for the leaching of gold and silver with cyanidic leaching solution and controlled addition of hydrogen peroxide
US5250272A (en) * 1988-09-09 1993-10-05 Degussa Aktiengesellschaft Process for leaching precious metals with hydrogen-peroxide and a cyanide leaching solution
US5215575A (en) * 1989-03-07 1993-06-01 Butler Dean R Recovery of gold, silver and platinum group metals with various leachants at low pulp densities
AU633203B2 (en) * 1990-06-02 1993-01-21 Degussa A.G. A process for leaching gold and silver
US5336474A (en) * 1990-06-02 1994-08-09 Degussa Aktiengesellschaft Process for leaching of precious metals
AU656899B2 (en) * 1990-08-16 1995-02-23 University Of The Witwatersrand Determining cyanide concentration
US5368830A (en) * 1992-10-15 1994-11-29 Calgon Corporation Scale control in gold and silver mining heap leach and mill water circuits using polyether polyamino methylene phosphonates
WO1997044793A1 (en) * 1996-05-21 1997-11-27 British Nuclear Fuels Plc Decontamination of metal
US6169221B1 (en) 1996-05-21 2001-01-02 British Nuclear Fuels Plc Decontamination of metal
US5961833A (en) * 1997-06-09 1999-10-05 Hw Process Technologies, Inc. Method for separating and isolating gold from copper in a gold processing system
US6355175B1 (en) 1997-06-09 2002-03-12 Hw Process Technologies, Inc. Method for separating and isolating precious metals from non precious metals dissolved in solutions
ES2163948A1 (es) * 1998-07-14 2002-02-01 Consejo Superior Investigacion Procedimiento hidrometalurgico para la recuperacion de oro de minerales y materiales metalicos.
US6406675B1 (en) * 2000-09-13 2002-06-18 Hercules Incorporated Method for reducing cyanide consumption during processing of gold and silver ores to remove base metals
US20050067341A1 (en) * 2003-09-25 2005-03-31 Green Dennis H. Continuous production membrane water treatment plant and method for operating same
RU2380434C1 (ru) * 2008-10-03 2010-01-27 Институт химии Дальневосточного отделения Российской академии наук (статус государственного учреждения) (Институт химии ДВО РАН) Способ извлечения золота из золотосодержащего органического сырья

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Publication number Publication date
NZ227675A (en) 1990-04-26
AU2679788A (en) 1989-07-27
BR8900199A (pt) 1989-09-12
EP0327695B1 (de) 1992-07-01
EP0327695A1 (de) 1989-08-16
AU604389B2 (en) 1990-12-13
ZA89137B (en) 1989-10-25
PH26633A (en) 1992-09-04
AR240176A1 (es) 1990-02-28
DE3801741C1 (enExample) 1989-06-15

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